The PT7(A1/O4/O3) is a promoter resulted from construction of O3 and O4 operators into PA1. a promoter derived from coliphage T7. that evidenced lower the occupancy of the promoter by RNA polymerase and thereby increases the repression factor. A new expression system. https://www.ivoryjinelle.com/limited-value-Hunting-Camo-iPhone-SE-2nd-3rd-Gen-Pro-Case-p79729-hot-value/